The present invention relates to an electrolyte for an electrolytic capacitor and the capacitor formed therewith.
There has been an ongoing demand forever smaller electrical components to support the continual drive to smaller devices. Of particular interest for the present invention is the demand for smaller, yet higher energy density, electrolytic capacitors. This demand has exhausted the current technical capabilities thereby requiring further advances in the art. Such an advance is provided herein.
Electrolytic capacitors, particularly tantalum-based capacitors, have been prepared utilizing aqueous solutions of ethylene glycol with ionogens such as acetic acid and phosphoric acid and ammonium acetate. Capacitors of this type are exemplified in U.S. Pat. No. 6,219,222. While these capacitors have historically fulfilled many of the necessary requirements electrolytes containing ethylene glycol are not as thermally and electrically stable as desirable.
It is an object of the present invention to provide an electrolyte containing a more stable organic solvent than ethylene glycol.
Polyethylene glycol dimethyl ethers have greater oxidation resistance, higher boiling points and lower viscosity than ethylene glycol.
These and other advantages, as would be realised to one of ordinary skill in the art, are provided in an electrolytic capacitor comprising an anode, cathode and an electrolyte, the electrolyte comprises an aqueous solution comprising a compound of formula 1:
CH3xe2x80x94(OCH2CH2)mxe2x80x94OCH3xe2x80x83xe2x80x83Formula 1
wherein m is an integer from 3 to 10. The electrolyte also comprises an ionogen.
Another embodiment is provided in an electrolyte for activating a capacitor. The electrolyte comprises water and about 10 to about 70%, by weight, a compound of formula 1:
CH3xe2x80x94(OCH2CH2)mxe2x80x94OCH3xe2x80x83xe2x80x83Formula 1
wherein m is an integer from 3 to 10. The electrolyte further comprises an ionogen and an acid.
Another embodiment is provided in an electrolytic capacitor. The capacitor comprises an anode of a valve metal and a metal oxide cathode. The capacitor further comprises an aqueous electrolyte comprising a compound of formula 1:
CH3xe2x80x94(OCH2CH2)mxe2x80x94OCH3xe2x80x83xe2x80x83Formula 1
wherein m is an integer from 3 to 10. The electrolyte further comprises about 0.05 to about 40%, by weight, ionogen and the electrolyte has a pH of about 1 to about 7.
A particularly preferred embodiment is provided in a method for providing a capacitor. The method comprises the steps of:
a) providing a tantalum anode;
b) providing a cathode;
c) activating the anode and the cathode with an electrolyte wherein the electrolyte comprises water; about 10 to about 70%, by weight, at least one compound of formula 1:
CH3xe2x80x94(OCH2CH2)mxe2x80x94OCH3xe2x80x83xe2x80x83Formula 1
wherein m is an integer from 3 to 10; about 0.05 to about 40%, by weight, ionogen; and optionally an acid.